It is well known that thermoplastic parts can be joined by heat welding. A common application of this knowledge is found in the construction of automobile interior panels and components such as sun visors which are constructed largely of thermoplastic components. Heat welding can be achieved by any of several technologies or methods including hot plate welding, hot air jet welding, laser welding and ultrasonic welding.
Hot plate welding, generally speaking, involves the application of a heated metal plate to the thermoplastic parts to be joined. A significant disadvantage in hot plate welding is the fact that thermoplastic material often sticks to the hot plate, resulting in filaments or streamers of material being drawn from the thermoplastic parts. This requires secondary cleanup operations to both the parts and the hot plate welder. Hot plate welding is also difficult or impossible to apply to small areas.
Hot air heating for thermoplastic fusion suffers the disadvantage of imprecise application; i.e., the hot air flows not only over the target area but also over surrounding areas and components which are undesirable to heat.
Laser heating suffers a number of disadvantages including high expense and the dangers which are inherently associated with stray laser radiation.
Ultrasonic welding is technically complex and requires not only an electroacoustic transducer but also a properly dimensioned horn which can be resonated.